LIDAR is an optical remote sensing technology that can measure the distance to or other properties of targets by illuminating the target with laser light and analyzing the reflected light.
For coherent LIDAR applications, LO laser light must be mixed with the diffuse laser light that is reflected by the remote target. A portion of the laser light produced by the LIDAR system transmitter is diverted and simultaneously projected onto a focal plane array (FPA) along with the reflected light. For many coherent LIDAR applications, the transmit laser light is fiber-based and launched into free space for transmission to the target. Therefore, the sampled LO light is also fiber-based.